Glomerular ultrastructure of the trout,Salmo gairdneri: Effects of angiotensin II and adaptation to seawater

Summary The effect of angiotensin infusion on the glomerular ultrastructure of freshwater- and seawater-adapted rainbow trout, Salmo gairdneri, has been examined by scanning and transmission electron microscopy. Adaptation of trout to seawater resulted in epithelial podocyte flattening, primary process broadening and apparent loss of foot processes in almost all glomeruli, features which were uncommon in freshwater-adapted trout. Similar changes were induced by infusion of freshwater-adapted animals with angiotensin, suggesting that the renin-angiotensin system plays a role in the modification of glomerular epithelial ultrastructure. Adaptation of trout to seawater also reduced glomerular diameter, but infusion of freshwater-adapted animals with angiotensin did not mirror this effect. Infusion of angiotensin into seawater-adapted animals increased the overall thickness of glomerular basement membrane by increasing the lamina rara interna and lamina densa. This did not occur when freshwater-adapted fish were either infused with angiotensin or adapted to seawater. These findings suggest that other humoral systems are involved in the control of glomerular diameter and basement membrane thickness as part of an integrated response to increased environmental salinity.     

Biochemical studies of soluble atrial natriuretic peptide (ANP) receptors from rat olfactory bulb and vascular smooth muscle cells

1. Aim. The biochemical characteristics of atrial natriuretic peptide receptors (ANP-R) derived from rat vascular smooth muscle (A-10 cell line) and central nervous system (CNS; olfactory bulb) tissue were compared. 2. Method and Results. ANP-Rs from each source were solubilized with 40 to 65% efficiency utilizing the nonionic detergent Lubrol-PX. Upon solubilization, the ANP-R from each source maintained the ability to bind 125I-ANP (99-126) with a high affinity; Scatchard analysis indicated that the VSMC ANP-R displayed a Kd for the radioligand of approximately 10 pM, whereas the olfactory receptor possessed a Kd of about 165 pM. The Bmax values for the soluble VSMC and olfactory ANP-Rs were 285 and 30 fmol/mg protein, respectively. Competition binding studies indicated that the VSMC ANP-R bound ANP(99-126), ANP(103-126), and ANP(103-123) with similar affinities, whereas the olfactory ANP-R was much more sensitive to changes in the COOH-terminal structure of the competing peptide. The soluble ANP-Rs from VSMC and olfactory were chromatographically indistinguishable on phenyl-, DEAE-, and wheat germ agglutinin-agarose columns. However, the ANP-Rs could be distinguished using GTP-agarose; the olfactory ANP-R was capable of binding to the resin, whereas the VSMC ANP-R was not. 3. Conclusions. Coupled with other studies, these data suggest that the A10 VSMC ANP-R observed in this study may not be coupled to guanylate cyclase and may represent a receptor serving a clearance function, whereas a significant proportion of the olfactory CNS ANP-R appears to be associated with GTP-binding proteins, likely particulate guanylate cyclase, and probably represents a coupled form of the receptor.     

Comparative efficiencies of bispecific F(ab′γ)2 and chimeric mouse/human IgG antibodies in recruiting cellular effectors for cytotoxicity via Fcγ receptors

Summary The three forms of Fc receptor carried by monocytes (FcRI, II) and natural killer (NK) cells (FcRIII) are all capable of mediating cell lysis. Here we compare the use of F(ab)₂ bispecific antibodies, specifically targetting individual FcR, and chimeric IgG mouse/human antibodies which are capable of targetting all FcR, for their ability to mediate target cell destruction. The derivatives are prepared by linking hinge sulphydryl residues via tandem thioether bonds, using a bismaleimide crosslinker: Fab from an anti-FcR mAb linked to Fab from a common anti-target mAb (BsAb), or Fab from the common anti-target mouse antibody linked to human Fc (FabFc or bisFabFc). All the derivatives targetting chick red blood cells gave efficient lysis, although different effector cell donors yielded differences in both the lytic levels achieved and the comparative efficiencies of derivatives. In contrast, significant lysis of the guinea pig lymphoblastic leukaemia, L₂C, regularly resulted only via the anti-FcRIII BsAb and the chimeric derivatives. These results suggest that the chimeric, Fc-containing derivatives mediate tumour cell lysis principally through FcRIII on NK cells. This is in contrast to the situation with the chick red blood cells where the chimeric derivatives appear capable of lysing erythrocytes by utilizing either monocytes or NK cells, because significant (50%) lysis occurred with effector cell populations magnetically depleted through either FcRII or FcRIII. A major difference between these two types of antibody derivative was their ability to function in the presence of high concentrations of normal human Fc. The lysis mediated by BsAb reactive with FcRI or II was unaffected by the presence of human Fc at 2.5 mg/ml (a concentration comparable with that yielded by IgG in plasma) whereas the BsAb recognizing FcRIII and all the Fc-containing derivatives were completely inhibited.This work has been supported by Tenovus, the Cancer Research Campaign, the Leukaemia Research Fund, Italfarmaco, Milano, Italy and the Imperial Cancer Research Fund     

Viral proteases as targets for chemotherapeutic intervention

Many viruses encode proteinases that are essential for infectivity, and are consequently attractive chemotherapeutic targets. The biochemistry and structure of the human immunodeficiency virus proteinase have been characterized extensively, and potent peptide-mimetic inhibitors have been developed. Techniques and strategies used to improve the efficiency of these compounds are likely to be applicable to other viral proteinases.     

Cytofluorometric analysis of anti-lymphocyte antibodies in AIDS

Abstract Anti-lymphocyte antibodies (ALA) have been detected in the plasma of 53.8% of HIV-positive patients tested (CD4/CD8 ratios: mean 0.265; range 0.01 to 0.5) using analytical continuous-flow cytofluorometry. IgG from the AIDS plasma was seen to bind to normal PBL in 53.8% of cases (14/26). In double labelling experiments CD4 + lymphocytes, CD8 + lymphocytes, and B lymphocytes were all bound by the ALA, but monocytes were not bound. Pre-adsorption of the diluted AIDS plasma onto an excess of mouse spleen cells did not remove lymphocyte binding activity. No evidence was found for preferential binding to phytohaemagglutinin-stimulated lymphocytes.
ALA could not be detected in the plasma of normal subjects, patients with acute renal failure undergoing renal dialysis, or patients with high levels of circulating immune complexes.     

Population Dynamics of Meloidogyne incognita and Rotylenchulus reniformis Alone and in Combination,and Their Effects on Sweet Potato

Meloidogyne incognita (Mi) and Rotylenchulus reniformis (Rr) interactions on sweet potato were studied in naturally and artificially infested field plots for 3 years. In a naturally infested field, early season counts of Mi or Rr were positively correlated with later counts of the same nematode, but negative correlations were found between early Mi and subsequent Rr, and early Rr and subsequent Mi counts. In field plots fumigated with methyl bromide and then infested with low levels of Rr, Mi, and Rr + Mi, final population densities of Mi juveniles were reduced by Rr, but Rr was not affected by Mi. In field plots with a high natural population density of Rr, artificial infestation with high levels of Mi in both fumigated and nonfumigated treatments inhibited Rr, while the final Mi juvenile population density was not affected. Results indicate that a competitive interaction exists with each species capable of inhibiting the other and becoming the dominant population. The nematodes had no apparent effect on yield at the inoculum densities used, either alone or mixed. Both nematodes increased cracking of sweet potatoes, but mixed populations did not differ in incidence of cracking from either Rr or Mi alone.     

Fine Structure Mapping in Yeast with Sunlamp Radiation

The X-ray mapping procedure of Manney and Mortimer (1964) is the most widely applicable and convenient method for fine structure analysis in yeast, but suffers the disadvantage that suitable X-ray machines or gamma ray sources are very expensive. Although many other recombinogens are known, none gives a linear dose-response like X-rays and few are as convenient or give as reproducible results. Experiments with Saccharomyces cerevisiae reported in this paper show, however, that the near-ultraviolet radiation emitted by fluorescent sunlamps gives linear dose-response relations, as reproducible results as ionizing radiations, and map distances which correlate highly with those obtained by using (60)Co gamma rays. It is suggested that this convenient recombinogen may be a suitable low-cost substitute for ionizing radiations in fine structure mapping.     

Grey seals, Halichoerus grypus, of the Dee Estuary and observations on a characteristic skin lesion in British seals

Grey seals on the West Hoyle Bank feed on a variety of fish and have a high incidence of dermal lesions, often associated with emaciation and nematode parasite infection. Corynebacterium phocae has been isolated from an active lesion. The significance of large numbers of seals in the Dee Estuary bearing lesions is discussed and the occurrence of seals with lesions elsewhere in British waters is reviewed. No evidence was found to associate the dermal lesions with any environmental factor and it is probable that lesions develop as a result of infection of minor wounds.     

FOWLER'S BACILLUS AND ITS PARASPORAL BODY

Fowler's bacillus is one of several organisms which form a non-viable inclusion or parasporal body during the process of sporulation. This body is globular and may be as large as or larger than the spore. Its position in the cell is not random; the spore is terminal and the body paracentral, lying between the spore and the remaining vegetative cell chromatin bodies. On completion of sporulation both spore and body are contained within an exosporium. The sequence in the development of the cell structures was followed in ultrathin sections of material fixed in permanganate. When sporulation is well advanced the body begins to grow from a single crystal, then presumably as a result of some disorientation in the growth process it develops as a multicrystalline body with the lattices orientated at different angles. When the body approximates the spore in size, a lamella coat is formed and an exosporium develops which eventually encircles the body and the spore. Other lamella systems microscopically similar to those surrounding the parasporal body develop free in the cytoplasm outside the exosporium. In both of these systems the number of lamellae is variable. The spore coat of Fowler's bacillus, consisting of an outer lamella layer and an inner unresolved amorphous layer has been found microscopically identical to the spore coat of B. cereus. In both organisms the lamella layer of the spore coat consists, in contrast to the other lamella systems, of a regular number of lamellae. Physiological tests would indicate that Fowler's bacillus is a variety of B. cereus.